The reforming of methane by carbon dioxide is studied over a Ni/La2O3 catalyst which presents an unusual catalytic stability compared to other nickel-based catalysts, A thorough TEM/EDX study combined with isotopic transient DRIFT and TAP experiments reveals the existence of a tight interface between a lanthanum carbonate phase and the nickel particles, A "bi-functional" mechanism is proposed to account for the observed kinetic behaviour : methane is activated on the Ni particles, carbon dioxide interacts with La2O3 to form carbonates which scavenge carbon from nickel at the Ni-La2O3 interface, thus restoring the Ni particles to their original state, This specific morphology of the active phase is also assumed to hinder the formation of deactivating coke, which explains the catalytic stability of such a catalyst.